Electrostatic charging apparatus



March 1954 c. F. ROBINSON ET AL 2,671,177

ELECTROSTATIC CHARGING APPARATUS Filed Sept. 4, 1951 CAPAC/T/VE LOAD /4CAPA C/T/VE LOAD l4 INVENTORJ; CHARLES F. ROBINSON ARI 0 A. LAHT/ ATrek/va Patented Mar. 2, 1954 ELECTROSTATIC CHARGING APPARATUS CharlesF. Robinson and Arvo A. Lahti, Pasadena, Calif., assignors toConsolidated Engineering Corporation, Pasadena, Calif., a corporation ofCalifornia Application September 4, 1951, Serial No. 244,992

1 This invention relates to an improved electrostatic generator forproviding an electric charge.

In radioactive surveying instruments it is necessary to charge acapacitive system to a high potential from a high impedance source.Ordinarily it is desirable to provide a manually driven generator forproducing the electric charge for such instruments so that theinstruments may be used in any location without requiring conventionalprimary sources of voltage such as batteries, power lines, ormotor-generator sets.

In accordance with the present invention, a manually operatedelectrostatic generator for producing a charge for a capacitive systemis provided in which a friction type generator is employed to produce anelectrostatic potential, and an induction type generator is employed to9 Claims. (Cl; 310-6) The rotor of the induction generator I2 comprisesa cylindrical disk 26 which is composed of a good insulating materialsuch as polystyrene, havinga plurality of conductive cylindricalsegments '28 secured to the periphery thereof. The rotor segments 28 areevenly spaced around the periphery of the disk 26, and they areinsulated from one another. The rotor segments 28 are convey an electriccharge from the friction generator to the capacitive load and to isolatethe friction generator from the capacitive load. Both the frictiongenerator and the induction generator are actuated by a single-crankwhich may be manually operated. The induction type electro-' staticgenerator is arranged so that the capacitive load is charged when thecrank is rotated in one direction and so that the capacitive load isdischarged at a low incremental rate when the crank is rotated in theopposite direction, thereby providing means for adjusting the amount ofcharge or the voltage which is applied to the capacitive load.

The invention will be explained with reference to the drawings, inwhich:

Fig. 1 is a schematic diagram of a preferred embodiment of the apparatusof the present invention; and

. Fig. 2 is a schematic diagram of a modification of the apparatus shownin Fig. 1.

The'apparatus disclosed in Fig. 1' comprises a friction generator I andan induction generator I2 arranged so that the friction generator I6serves to provide a charge on the inducing electrode of the inductiongenerator I2 and so that the induction generator I2 serves to convey acharge to a capacitive load I4.

The friction generator I6 comprises a rotor l6 which is a cylindricaldisk composed of a good insulating material such as polystyrene oramber. A grounded charging brush is secured in intimate contact with therotor I6 by means of a spring I1 and the charging brush comprises acylindrical conductive member I8 having a facing 20 composed of asemi-conducting material such as leather or nylon, which is capable ofinducing a charge by friction on the rotor I6. A conductive collectingbrush 22 engages the rotor It on the side opposite the charging brush.

A cylindrical stator plate 24, which is electrically connected to thecollecting brush 24, serves as the inducing electrode for the inductiongenerator I2.

slightly shorter than the stator plate 24, and are so arranged that therotor plates 28 are caused to rotate past the stator plate 24 when thedisk 26 is rotated. Two grounded brushes 3!! and 32 make contact withthe rotor segments 28 when the member 26 is rotated, and the brushes aredisposed so that the brush 36 makes contact with the rotor segments 28as they pass in close proximity to the stator plate 24 and so that thebrush 32 makes contact with the rotor segments 28 at some angularlocation wherein the rotor segments are out of mesh with the stator 24.A collector brush 34 also makes contact with the rotor segments 28 atanother angular location wherein the respective rotor segments which arecontacted by the brush 34 are out of mesh with the stator 24. The threebrushes 30, 32 and 34 are so arranged that no two brushes ever makecontact with the same rotor section simultaneously.

A crank 36 is employed to drive the two rotors I6 and 26 simultaneouslythrough shafts 38 and 40, a system of pulleys 42 and 44, and a belt 46.

When the crank 36 is turned clockwise the friction generator I6 servesto produce a charge on the stator plate 24, since the stator plate 24and the respective grounded rotor segments 26 which mesh with the statorplate 24 provide capacitances which are successively connected in seriesacross the output of the induction generator III. Thus, each rotorsegment 28 which meshes with the stator plate 24 has a charge induced onit which is equal to but of opposite polarity with respect to the chargeon the stator plate 24, the charge on the rotor segment 26 being drawnfrom ground through the brush 30.

As each charged rotor segment 28 is rotated in a clockwise direction,the ground connection is broken while the rotor segment is stillpartially in mesh with the stator 24, and hence the charge remains onthe rotor segment until the rotor segment contacts the collector brush34. Since a capacitive load I4 is connected between the brush 34 andground, a portion of the electric charges on the rotor segments 28 istransferred to the capacitive load I4, and if the capacitance of theload I4 is large with respect to the capacitance of the individual rotorsegments 28 to ground when they are in mesh with the stator plate 24,all but a small fraction of the charges on the rotor segments 28 will betransferred to the load I4.

When the crank 36 is turned in a counterclock- 3 wise direction, acharge is similarly induced on the rotor segments 28. However, thegrounded brush 3! makes contact with the rotor segments pacitive chargedivision relations. Since the capacitance between the rotor segments IIand groundissmallwithreepecttothecapacitance oitheload,onbasmallincrementoithe chargeoithecapacitiveloadllisdrawnoiiwhen arotor segment is contactsthe brush it while rotating in acounterclockwise direction.

Thus, a capacitive load it, such as an ionization chamber tor aradioactive surveying instrument, may be charged by manually turning thecrank 8| in a clockwise direction, and ii the capacitive load It isovercharged, small increments or the charge may be removed by manuallyturning the crank it in a counterclockwise direction. Accordingly, theapparatus shown in Fig. 1 provides means for accurately controlling theamount of charge, and hence the voltage, which is applied'to thecapacitive load ll.

The-modification oi the invention which is disclosed in Pig. 2 providesa charge which is either positive or negative with respect to ground, or

if desired, the apparatus may be employed to 7 provide positive andnegative charges to separate a loads.

The i'riction type generator II is the same as that disclosed in Fig. l.

The induction type generator I! diflers from that shown in Fig. l inthat the length of the rotor segments 28' is less than half the lengthor the stator plate It. An additional stator plate it is provided, andtwo fixed brushes 52 and it, which are connected by a conductor 50,provide a short circuit between two diametrically opposed rotor ments(which are in mesh with the respective stator plates 24' and II. Twofixed brushes I8 and 60, which engage diametrically opposed rotorsegments at some angular location wherein the rotor segments 28' are notin mesh with the stator sections 2,4 and ll, are connected together andto ground by a conductor ll.

A pair of collector brushes 2 and 64 which engage diametrically opposedrotor segments II are employed to convey the electric charges on therotor segments 20' to the capacitive load It.

In the embodiment of the invention shown in Fig. 2, a switch 60 isemployed to connect either oi the collector brushes '2 and 64 to theload It,

thereby permitting the application oi either a positive or a negativecharge to the load It.

polarity may be applied to the load ll, through the switch It.

Whentherotora ltandll'arerotatedina clockwise direction. the groundedbrushes It and I serve to cause the charges on the rotor segments IItorlowto ground berore they reachthe collector brushes I! and it. Asbefore, when the discharged rotor segments 2| make contact with thecollector brushes, a portion of the charge of the capacitive load isdrawn oil, thereby providing means for accuratel controlling the amountor charge on the capacitive load it.

It will be apparent that the apparatus disclosed herein may be employedto charge capacitive systems other than those employed in radioactivesurveying instruments provided the average current drain of thecapacitive system is very low.

It will be apparent that the apparatus shown in 2 may be employed toapply a positive charge to one capacitive load and a negative charge toanother capacitive load, if desired.

When the rotors II and it are rotated in a counterclockwise direction,the friction generator ll serves to produce a charge on theinterconnected rotor segments 28' which are in mesh with the statorplates 24' and it as shown in Fig. 2, since these rotor segments and thestator plates 24' and it provide two capacitances which are connected inseries across the output at the induction generator III. This chargeremains on the rotor segments until they contact the collector brushesl2 and N, whereupon the charges oi one We claim: l. Electrostaticapparatus a pinrality of spaced conductive members located aroimd anaxis, conductive means located in the proximity oi the conductivemembers for providing an electrostatic inductive coupling to theconductive members when they are in mesh therewith, means for rotatingthe conductive members around said axis and causing the conductivemembers to mesh with the conductive means in sequence, means forapplying an electrostatic voltage between the conductive means and eachof the conductivemembersduring a portion oi the periods when each oi theconductive members is in mesh with the conductive means, means forcollecting the electrostatic charges which are induced on the conductivemembers when they are rotated in one direction, and means fordischarging the electrostatic charges which are induced on theconductive members when they are rotated in the other direction.

2. Electrostatic apparatus comprising a rotatable disk having aplurality of evenly spaced conductive members secured to the peripherythereof and electrically insulated from one another, conductive meanslocated adjacent to the periphery of the disk for providing anelectrostatic inductive coupling to the conductive members when they arein mesh therewith, means for rotating the disk' and causing theconductive members to mesh with the conductive means in sequence, meansfor applying an electrostatic voltage between said conductive means andeach or the conductive members during a portion 0! the periods when eachot the conductive members is in mesh with the conductive means,

.means for collecting the electrostatic charges which are induced on theconductive members when the disk is rotated in one direction, andgrounded means separate from the collecting means for discharging theelectrostatic charges on the conductive members when the disk is retatedin the other direction.

3. The apparatus or claim 2, wherein the conductive means comprises apair'oi inducing electrodes located at diilerent angular positionsaround the periphery or the disk, and wherein the means ior apply n anelectrostatic voltage between the conductive means and each of theconductive members comprises an electrostatic generator having itsoutput circuit connected to the two inducing electrodes, and a conductorwhich successively interconnects pairs of the able disk. a plurality ofevenly spaced conductive memberssecuredtothepcripheryoithediskandelectrically insulated from one another, a pair of inducing electrodeslocated on diametrically opposite sides of the disk adjacent to theperiphery thereof, means for rotating the disk and causing theconductive members to mesh with the inducing electrodes in sequence, anelectrostatic generator having its output circuit connected between thepair of inducing electrodes, fixed conductive means for providing asliding contact between pairs of the conductive members which arelocated on diametrically opposite sides of the disk during a portion ofthe periods when the pairs of conductive members are in mesh with theinducing electrodes, a pair of collector brushes located ondiametrically opposite sides of the disk for collecting theelectrostatic charges which are induced on the conductive members whenthe disk is rotated in one direction, and a pair of grounded brusheslocated on diametrically opposite sides of the disk intermediate thecollector brushes and the inducing electrodes for discharging theelectrostatic charges on the conductive members when the disk is rotatedin the opposite direction.

5. Electrostatic apparatus comprising a first conductive member, aplurality of spaced conductive members located around an axis andadapted to be rotated adjacent to and past said first conductive memberand thereby mesh with the first conductive member in sequence, means forapplying a voltage between the first conductive member and each of themembers of said plurality of conductive members during a portion of theperiods when the members of said plurality of conductive members are inmesh with said first conductive member, a collector means for contactingeach of the members of said plurality of conductive members in sequenceas said plurality of conductive members are rotated, and 'a groundedmeans separated from the collector means for contacting each of themembers of said plurality of conductive members in sequence as saidplurality of conductive members are rotated.

6. Electrostatic apparatus comprising a nonconductive rotatable disk, aplurality of spaced conductive members secured to the periphery of thedisk, an inducing electrode located adjacent to the periphery of saidrotatable-disk for providing an electrostatic inductive coupling to theconductive members when they are in mesh with the inducing electrode,means for applying a voltage between said inducing electrode and each ofthe conductive members during a portion of the periods when each of theconductive members is in mesh with the inducing electrode, a collectorelectrode for contacting each of the conductive members in sequence asthe rotatable disk is rotated, and a grounded electrode spaced from thecollector electrode for also contacting each of the conductive membersin sequence as the rotatable disk is rotated.

7. Electrostatic charging apparatus comprising a non-conductiverotatable member having a plurality of evenly spaced conductive membersof the same size secured thereto, an inducing eiectrode located adjacentto the periphery of the rotatable member for providing an electrostaticinductive coupling to the conductive members when they are in meshwith'the inducing electrode, the inducing electrode being larger thanthe members of said plurality of conductive members, a brush forproviding a sliding contact with each 0! the conductive members when itis in mesh with the inducing electrode, an electrostatic generatorhaving its output circuit connected to the brush and the inducingelectrode, and means for providing a sliding contact with each of theconductive members in sequence as the rotatable member is rotated.

8. Electrostatic apparatus comprising a nonconductive rotatable memberhaving a plurality of evenly spaced cylindrical conductive members ofthe same size secured thereto, a cylindrical inducing electrode locatedadjacent to the periphery of the rotatable member for providing anelectrostatic inductive coupling to the members of said plurality ofconductive members when they are in mesh with the inducing electrode,the inducing electrode having a length along the plane of rotation 01'the rotatable member which is greater than the length of each of theconductive members along the plane of rotation of the rotatable member,a brush for providing a sliding contact with each member of saidplurality of conductive members during a portion of the periods when themember is in mesh with the inducing electrode, an electrostaticgenerator having its output circuit connected to the brush and theinducing electrode, means for providing a sliding contact with each ofthe members of said plurality of conductive members in sequence as therotatable member is rotated, and grounded means for providing a furthersliding contact with each of the members of said plurality of conductivemembers in sequence as the rotatable member is rotated.

9. Electrostatic apparatus comprising a rotatable member having aplurality of evenly spaced conductive members of the same size securedthereto and electrically insulated from one another, a furtherconductive member located adjacent to the periphery of and in the plane01' rotation of said rotatable member for providing an electrostaticinductive coupling to the members of said plurality of conductivemembers when they mesh with the further conductive member, the length ofsaid further conductive member along the plane of rotation of therotatable member being larger than the length oi the members of saidplurality of conductive members along the plane of rotation of saidrotatable member, a charging electrode for providing a sliding contactwith each member of said plurality of conductive members when it mesheswith the further conductive member, an electrostatic generator havingits output circuit connected'to the charging electrode and said furtherconductive member, a collector electrode for providing a sliding contactwith each of the members of said plurality of conductive members insequence as said rotatable member is rotated, and a grounded electrodeseparated from the collector electrode for providing a further slidingcontact with each of the members of said plurality of conductive membersin sequence as said rotatable member is rotated.

CHARLES 1". ROBINSON. ARVO A. LAHTI.

References Cited in the tile 0! this patent UNITED STATES PATENTS Number

